The UK's Ancient Monuments and Archaeological Areas Act 1979 makes it a criminal offence to destroy or damage a scheduled monument. Scheduled Ancient Monuments still sometimes get 'trashed', however, and this time a large part of one of the Priddy Circles (Somerset, England) has been bulldozed into the ground.
The four Neolithic henges trace a line across the landscape of the Mendip Hills south of Bristol, close to the linear barrow cemeteries of Ashen Hill and Nine Barrows.
The southern circle was the best preserved of the four, with most of its ditch and bank easily visible. Now, taking the circle as a clock dial with the north at 12 o'clock, there is nothing left of either the ditch or the bank between about 4 o'clock (ESE) and 8 o'clock (WSW). It appears from the tracks and the re-seeding that it was done using a bulldozer not many weeks ago.
There are two massive heaps of stones in the field, one comprising modern builders' rubble and one just stones. It's possible that the latter came from the core of the henge wall.
A stone wall on the eastern boundary of the field bisects the circle so the destruction stops at this point, leaving the portion of the circle on the neighbouring land untouched. The effect is to expose cross sections of the henge wall within the stone boundary wall.

Edited from The Megalithic Portal (19 June 2011), The Heritage Journal (21 and 23 June 2011)